1. Field of the Invention
This invention relates to an apparatus for imaging fluorescent particles, and more particularly to an apparatus for imaging fluorescent particles such as leukocytes or the like stained with a fluorescent dye.
2. Description of the Prior Art
In the medical field, platelet preparations and erythrocyte preparations are produced by extracting platelets and erythrocytes from whole blood. These platelet and erythrocyte preparations are each used for blood transfusions, and it is undesirable for either preparation to contain leukocytes. It is therefore important to be able to know how many leukocytes the preparations contain. Conventionally this is done by placing a sample platelet preparation in a NAGEOTTE chamber, staining with a fluorescent dye, projecting an excitation light onto the sample and counting leukocytes via a microscope. Specifically, a 50 microliter sample is taken from a 200 or 400 milliliter bag of platelet preparation, the leukocytes in the sample are counted and converted to a leukocytes count for the whole bag. This is a tiring, inefficient, time-consuming task that has to be done by skilled personnel.
An apparatus has been proposed to enable leukocytes to be counted, instead, by staining the leukocytes with a fluorescent dye, illuminating the sample with an excitation light having predetermined wavelengths, using a CCD camera or the like to image the sample and then analyzing the images to obtain a count of the leukocytes. However, the solution containing the stained leukocytes also contains fluorescent dye that also emits fluorescent light. Thus, since not only the stained leukocytes but also the fluorescent dye itself is excited by the excitation light, there is a marked decrease in the contrast of the leukocytes that it is desired to observe or image. In some cases, the contrast may worsen to the point that the leukocyte images become so buried in the background that they cannot be picked out, making it impossible to count the leukocytes.
An object of the present invention is to provide an apparatus for imaging fluorescent particles that enables the fluorescent particles to be well imaged by reducing the effect of background light.